Generally, a transmission device for an automobile engine and the like to perform power transmission by the power transmission medium such as a chain has a guide for the transmission device, such as a fixed guide or a movable guide, to perform sliding of the power transmission medium attached to a body frame such as an engine block wall with bolts or the like. The movable guide such as a tensioner lever or the like used for such a transmission device applies appropriate transmitting tension to the power transmission medium in order to prevent transmission failure due to excess stretching or excess loosening of the circulation-traveling power transmission medium. And, the fixed guide such as a guide rail limits the circulation-traveling power transmission medium to a predetermined path of travel in order to prevent the power transmission medium from producing vibration noise and to prevent sideward vibration and disengagement.
FIG. 4(a) is a front view, and FIG. 4(b) is a sectional view taken along line A-A of FIG. 4(a), showing a conventional plastic guide (a tensioner lever) for a transmission device. This plastic guide 40 for a transmission device is formed of a single synthetic resin as a movable guide for a transmission device having a chain as the power transmission medium, and comprised of a slide rail 41, which is in slide contact with a traveling chain C, and a rail support 42. And, the rail support 42 is formed to have a boss portion 42a having a mounting hole 43 which serves to attach to an engine block wall and functions as a movable guide, a tensioner abutting portion 42b which abuts a tensioner (not shown) for applying appropriate tension to the chain, and reinforcing ribs 42c which serve to reinforce and also to reduce the weight.
But, the conventional plastic guide 40 for a transmission device is integrally formed of a single synthetic resin, so that it is hard to keep at a high level both of the sliding contact property and wear resistance that the slide rail 41, with which the chain C is in sliding contact, is required to possess and the strength property that the rail support 42 supporting the slide rail 41 is required to possess. For example, when the plastic guide 40 for a transmission device is formed of only plastic having an excellent sliding contact property and wear resistance, there are disadvantages that mechanical strength is poor, and if a section size is increased in order to compensate for the lack of the strength, the guide has an increased thickness to have a large size, and the space occupied by the guide when it is attached to the engine block wall becomes large.
As a plastic guide for a transmission device which remedies the above-described problems, there is, for example, Patent Literature 1 that proposes a sandwich-molded guide for a transmission device, wherein a slide rail is formed of a material having as the principal component a first high polymer material having wear resistance and heat resistance, and a rail support is formed of a material having as the principal component a second high polymer material having a strength higher than that of the material having as the principal component the first high polymer material. And, the slide rail and the rail support are integrally formed in an intimately joined state to each other by injection molding by a sandwich molding process, and the surface layer portions of the slide rail and the rail support are fully coated with the material having the first high polymer material as the principal component.
[Patent Literature 1]
Japanese Patent Laid-Open Publication No. 2002-372111